Add tox test matrix, Makefile targets, and dev extra

Makefile

@@ -0,0 +1,19 @@
+.PHONY: test install install-test test-tox clean
+
+test:
+	pytest
+
+install:
+	pip install -e .
+
+install-test:
+	pip install -e '.[test]'
+
+# test-tox runs the suite on every supported interpreter (2.7 and 3.7); Jenkins CI invokes this target.
+test-tox:
+	tox
+
+clean:
+	rm -rf .pytest_cache .tox build dist *.egg-info
+	find . -name '*.py[co]' -delete
+	find . -name __pycache__ -type d -prune -exec rm -rf {} +

README.rst

@@ -13,7 +13,7 @@ Requirements
 * pylibmc
 * Django 1.5+.
 
-It was written and tested on Python 2.7 and 3.4.
+It was written and tested on Python 2.7 and 3.7.
 
 Installation
 ------------
@@ -169,3 +169,9 @@ Install the test dependencies and run the tests like this::
 
     pip install -e '.[test]'
     pytest
+
+To run the suite across the supported Python versions (2.7 and 3.7), use tox::
+
+    tox
+
+These steps are also wrapped in the Makefile as ``make install-test``, ``make test``, and ``make test-tox``.

setup.py

@@ -23,6 +23,8 @@
             "pytest>=4.6; python_version >= '3.0'",
             "mock; python_version < '3.0'",
         ],
+        # Orchestration tooling for the outer env. tox builds and runs the per-version test envs.
+        "dev": ["tox"],
     },
     classifiers=[
         'Development Status :: 4 - Beta',

tox.ini

@@ -0,0 +1,14 @@
+[tox]
+envlist = py27, py37
+skip_missing_interpreters = False
+
+[testenv]
+# Pin Django to the 1.11 series this package targets, the last release that runs on both 2.7 and 3.7
+# and still ships smart_text and PyLibMCCache that the backend imports.
+deps = Django>=1.11,<2.0
+setenv =
+    PYTHONPATH = {toxinidir}
+commands =
+    pip install -U pip
+    pip install -e .[test]
+    pytest --basetemp={envtmpdir}